United States vehicle emission standards
United States vehicle emission standards are set through a combination of legislative mandates enacted by Congress through Clean Air Act (CAA) amendments from 1970 onwards, and executive regulations managed nationally by the Environmental Protection Agency (EPA), and more recently along with the National Highway Traffic Safety Administration (NHTSA).
The Clean Air Act of 1963 (CAA) was passed as an extension of the Air Pollution Control Act of 1955, encouraging the federal government via the United States Public Health Service under the then-Department of Health, Education, and Welfare (HEW) to encourage research and development towards reducing pollution and working with states to establish their own emission reduction programs.
[1] By 1967, this authority empowered the federal government to establish enforceable emission standards, setting a precedent for addressing transportation-related air pollution on a national scale.
[2] In the mid-20th century, California's economy grew rapidly after the Great Depression, but this economic development was accompanied by an increase in air pollution in the state.
As a result, smog started to form in the valleys of Southern California, causing respiratory problems for humans and damaging crops.In the 1960s, Dutch chemist Arie Jan Haagen-Smit identified the air pollutants responsible for the smog: carbon monoxide, hydrocarbons, and nitrogen oxides emitted from cars and factories through inefficient fuel combustion.
Among other key provisions was the establishment of required vehicle inspection and maintenance programs (I/M) in nonattainment states and optional in other areas.
Other states that had met the NAAQS attainment goals could optionally establish I/M programs for existing but were required to follow the EPA's specifications.
Two sets, or tiers, of emission standards for light-duty vehicles in the United States were defined as a result of the Clean Air Act Amendments of 1990.
California's Low-emission vehicle (LEV) program defines six automotive emission standards which are stricter than the United States' national Tier regulations.
A set of transitional and initially voluntary "national low emission vehicle" (NLEV) standards were in effect starting in 1999 for northeastern states and 2001 in the rest of the country until Tier II, adopted in 1999, began to be phased in from 2004 onwards.
Instead of basing emissions on vehicle weight, Tier II standards are divided into several numbered "bins".
A second round of California standards, known as Low Emission Vehicle II, is timed to coordinate with the Tier 2 rollout.
[15] Heavy-duty vehicles must comply with more stringent exhaust emission standards and requires ultra-low sulfur diesel (ULSD) fuel (15 ppm maximum) beginning in 2007 model year.
The EPA faced a lawsuit seeking to compel it to regulate greenhouse gases as a pollutant, Massachusetts v. Environmental Protection Agency.
As of 2007, the California Air Resources Board passed strict greenhouse gas emission standards[17] which are being challenged in the courts.
A group of automakers including General Motors, DaimlerChrysler, and the Alliance of Automobile Manufacturers had sued the state of Vermont to block rules calling for a 30 percent reduction in GHG emissions by 2016.
Members of the auto industry argued that complying with these regulations would require major technological advances and raise the prices of vehicles as much as $6,000 per automobile.
"The court remains unconvinced automakers cannot meet the challenge of Vermont and California's (greenhouse gas) regulations," he wrote.
[25] After Donald Trump was inaugurated as president in 2017, he instructed the NHTSA and EPA to rollback Obama's CAFE standards, increasing the 2026 target to a then-projected 202 g CO2/mi and requiring only an annual 1.5% fleet efficiency improvement.
The Trump administration argued the rollback was required due to the increasing costs of cars on consumers that higher efficiencies would only make more expensive.
[25] Following Joe Biden becoming president in 2021, he signed Executive Order 14057, "Catalyzing Clean Energy Industries and Jobs Through Federal Sustainability", which in addition to committing the federal government to implement clean transport options such as EVs, also committed to improving the fuel efficiency standards and reversing the Trump administration's actions.
[26] The EPA issued a new rule in December 2021, to become enforceable by February 2022, that effectively restored the Obama-era standards, through decreasing the fleet-wide emissions target to a projected 161 g CO2/mi by the 2026 model year.
[29] California applies for this waiver through the EPA, which publishes the proposed standards for public review in the Federal Register.
[30] Since the CAA's passage in 1967, California has applied and received more than fifty waivers, which include emission standards across various vehicle classes.
100% ZEV mandate by 2035, includes up to 20% of PHEVs by referring them as TZEV (Transitional Zero Emission Vehicle) and rest of the proportion with BEVs and FCEVs.
[43] As part of Trump's "Safer, Affordable, Fuel-Efficient" (SAFE) program, the EPA and NHTSA proposed a new "One National Program Rule" that asserted that only the federal government may set emissions standards on September 19, 2019, as to have one consistent set of fuel emission and mileage standards across the country.
[46] Following the election of Joe Biden as president, the EPA and NHTSA moved to reverse the 2019 rule in April 2021, thus returning to the previous status quo for California.
After completion of the schedule, the computerized system calculates the emissions from the car and determines if it meets the appropriate specification for its model year.
Since model year 1994, all LDV and LDT manufactured for use in the United States are required to use the standard on-board diagnostic OBD-II system.
It will warn the operator if the OBD-II determines significant deviations from expected emissions control standards, indicating repairs may be needed.
